Mechanism for a Chair

ABSTRACT

The mechanism which is designed for a chair, in particular for a rotatable office chair with a gas spring which is arranged in a vertical manner in the lower frame of said chair and has a telescopically extendable piston rod for adjusting the height of a seat, has the effect that the adjustment of the inclination of the seat is synchronous with the adjustment of the inclination of the backrest. The mechanism has a base ( 20 ) which is stationary per se, through which a stationary first rotary shaft (D 1 ) extends and on which a seat support which can be inclined is mounted. A front connecting means ( 21 ) which is connected in an articulated manner in a stationary third rotary shaft (D 3 ) on the base ( 20 ) and in a moveable fourth rotary shaft (D 4 ) is arranged between the base ( 20 ) and the seat support. The mechanism also has a rear connecting means ( 24 ) which is connected in an articulated manner in a moveable sixth rotary shaft (D 6 ) at one end and in a further moveable rotary shaft (D 5 ) at the other end. The mechanism contains at least one first spring element ( 26 ) which acts between the base ( 20 ) and the seat support and is connected in an articulated manner in the fourth rotary shaft (D 4 ). At the other end, this first spring element ( 26 ) is connected in an articulated manner in a moveable eighth rotary shaft (D 8 ) whose position can be varied by means of a gear mechanism ( 25 ) which can be operated by the user from the outside. The first spring element ( 26 ) is advantageously a gas spring which can be blocked by means of a locking element ( 218 ) which can be operated by the user and with which the seat and backrest are locked in the in-operative position.

FIELD OF THE INVENTION

The invention relates to a chair mechanism, in particular for a rotatable office chair with a pneumatic spring which is arranged vertically in the substructure and is intended for adjusting the height of the seat. As a result of the chair mechanism, the seat surface is lowered in the rearward direction synchronously with the rearward inclination of the backrest, which the user initiates by shifting his weight.

PRIOR ART

Many synchronizing mechanisms for chairs are known, e.g. from patent publications EP 0 592 369 B1, EP 0 839 478 B1, EP 1 039 816 B1, EP 1 358 821 A1 and WO 2005/120291 A1, and have become a standard feature for comfortable commercially available chairs for the workplace.

OBJECT OF THE INVENTION

In relation to the known prior art, it is an object of the invention to propose a further-improved chair mechanism which responds more sensitively to shifts in weight. A further object is to facilitate the adjustment of the prestressing of the mechanism for relatively light and relatively heavy individuals. An additional object is to render the mechanism more universal, in order to make it possible for a backrest and armrest to be attached in different ways.

OVERVIEW OF THE INVENTION

The mechanism is intended for a chair, in particular for a rotatable office chair with a pneumatic spring which is arranged vertically in the substructure and has a telescopically extensible piston rod for adjusting the height of a seat. The inclining adjustment of the seat is synchronous with the inclining adjustment of a backrest. The mechanism has a fixed base, through which a fixed first axis of rotation extends and on which an inclinable seat carrier is mounted. Arranged between the base and the seat carrier is a front connecting means, which is articulated along a fixed third axis of rotation on the base and along a movable fourth axis of rotation. A rear connecting means is articulated, on the one hand, along a movable sixth axis of rotation and, on the other hand, along a movable further axis of rotation. The mechanism contains at least one first spring element which acts between the base and the seat carrier and is articulated along the fourth axis of rotation. The first spring element is also articulated along a movable eighth axis of rotation, which can be changed in position by means of a gear mechanism which can be actuated by the user from the outside.

Specific embodiments of the invention will be defined hereinbelow: the gear mechanism is articulated along a fixed second axis of rotation, which extends through the base, along the eight axis of rotation and along a movable ninth axis of rotation. In the rest position, with the seat positioned, at least in principle, horizontally and the backrest located vertically, the second axis of rotation, the eighth axis of rotation and the ninth axis of rotation are located at least essentially vertically one above the other. In the relaxed position, with the seat inclined up to a maximum extent and the backrest inclined up to a complementary maximum extent, the eighth axis of rotation is displaced, in the direction of the third axis of rotation, in front of the second axis of rotation and the ninth axis of rotation moves, in the opposite direction, behind the second axis of rotation.

The first spring element is a pneumatic spring with a cylinder and a telescopically extensible piston rod which is extended to the greatest extent in the rest position, with the eighth axis of rotation moved all the way downward, and is retracted to the greatest extent in the relaxed position, with the eighth axis of rotation moved all the way upward. The piston rod is articulated along the fourth axis of rotation by means of an intermediate component.

The mechanism contains, within it, pairs of spring units which are supported, on the one hand, in a bearing of the base, and, on the other hand, beneath bearing strips, in bearing blocks, the bearing strips being joined to the base from both sides. The bearing strips preferably consist of plastic and thus form self-lubricating bearing locations along with the joined-on, preferably metallic components.

The front connecting means is designed as a plate-like lever, through which the third and fourth axes of rotation extend. The rear connecting means comprises a sixth axial rod and a sleeve component, which is connected thereto via arms, or a sixth axial rod and a seventh axial rod, which is connected thereto via arms, the associated fifth, sixth and seventh axes of rotation extending through these axial rods.

A backrest carrier can be articulated along the first axis of rotation, within the base, or a pair of side members can be articulated outside the base, in order for the backrest to be fastened thereon. The bearing strips have stubs for penetrating into the front lever and the intermediate component. The bearing strips also have mounts for accommodating the ninth axial rod, which passes through the gear mechanism, and for accommodating the sixth axial rod.

An arresting element, which can be actuated by the user, is arranged on the intermediate component for blocking the pneumatic spring with optional switching functions. The arresting element acts on a valve stem which is guided in the piston rod of the pneumatic spring.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the drawings:

FIG. 1A shows a perspective view from beneath of a chair with the mechanism according to the invention, using side members;

FIG. 1B shows a side view of the chair according to FIG. 1A in the rest position;

FIG. 1C shows a side view of the chair according to FIG. 1A in the relaxed position;

FIG. 2A shows an exploded view of the essential subassemblies of the mechanism;

FIG. 2B shows an exploded view of the variants for the backrest carrier, backrest levers and upholstery panel and also a pair of side members;

FIG. 3A shows a perspective view from above of a base with a plurality of axial rods;

FIG. 3B shows a perspective view from beneath of the base according to FIG. 3A;

FIG. 4A shows a perspective view from above of a front lever;

FIG. 4B shows a perspective view from beneath of the front lever according to FIG. 4A;

FIG. 5A shows a perspective view from beneath of a seat carrier;

FIG. 5B shows a perspective view from above of the seat carrier according to FIG. 5A;

FIG. 6A shows an exploded view of a gear mechanism with bolts and pneumatic spring mounted thereon;

FIG. 6B shows the arrangement according to FIG. 6A in the partially assembled state;

FIG. 6C shows a perspective view of the arrangement according to FIG. 6A in the assembled state;

FIG. 6D shows a different perspective view of the arrangement according to FIG. 6C;

FIG. 7A shows a spring unit in the assembled state;

FIG. 7B shows an exploded view of the spring unit according to FIG. 7A;

FIG. 8A shows a perspective view from beneath of a pair of bearing strips;

FIG. 8B shows a perspective view from above of the bearing strips according to FIG. 8A;

FIG. 9A shows a perspective view from above of a first variant of a backrest carrier, with axial rods;

FIG. 9B shows a perspective view from above of a second variant of a backrest carrier, with axial rods;

FIG. 10A shows a perspective view of a first variant of backrest lever, with bushings;

FIG. 10B shows a perspective view of a second variant of backrest lever, with bushings;

FIG. 10C shows a perspective view of a pair of side members;

FIG. 11A shows a perspective view from above of an upholstery panel, which is non-adjustable;

FIG. 11B shows a perspective view from above of an upholstery panel, which is adjustable;

FIG. 11C shows a perspective view from beneath of the upholstery panel according to FIG. 11B;

FIG. 12A shows a perspective view from above of a front lever with pneumatic spring and intermediate component inserted;

FIG. 12B shows a perspective view from beneath of the arrangement according to FIG. 12A;

FIG. 13A shows the mechanism in a first construction phase, with a first variant of backrest carrier;

FIG. 13B shows the mechanism in a second construction phase, with a first variant of backrest carrier;

FIG. 13C shows the mechanism in a third construction phase, with a first variant of backrest carrier;

FIG. 13D shows the mechanism in a fourth construction phase, with a first variant of backrest carrier and backrest lever in each case;

FIG. 13E shows the mechanism in a fifth construction phase, with a first variant of backrest carrier and backrest lever in each case;

FIG. 13F shows the mechanism in a sixth construction phase, with a first variant of backrest carrier and backrest lever in each case;

FIG. 13G shows a different perspective view of the arrangement according to FIG. 13F;

FIG. 13H shows a perspective view from beneath of the arrangement according to FIG. 13F;

FIG. 14A shows the mechanism with a second variant of backrest carrier and a first variant of backrest lever;

FIG. 14B shows a perspective view from above of the arrangement according to FIG. 14A, with the seat carrier completed;

FIG. 14C shows a perspective view from above of the arrangement according to FIG. 14B, with a backrest completed;

FIG. 14D shows a perspective view from beneath of the arrangement according to FIG. 14C;

FIG. 15A shows an exploded view of the mechanism with a second variant of backrest lever and with a pair of side members;

FIG. 15B shows the arrangement according to FIG. 15A in the assembled state;

FIG. 15C shows a perspective view from beneath of the arrangement according to FIG. 15B, completed with a seat carrier;

FIG. 16A shows a vertical section through the mechanism with a second variant of backrest carrier, in the rest position, as a functional principle;

FIG. 16B shows an offset vertical section through the arrangement according to FIG. 16A;

FIG. 16C shows a further offset vertical section through the arrangement according to FIG. 16A;

FIG. 16D shows a diagram of the axes in the rest position;

FIG. 17A shows a vertical section through the arrangement according to FIG. 16A, in the relaxed position, as a functional principle;

FIG. 17B shows an offset vertical section through the arrangement according to FIG. 17A;

FIG. 17C shows a further offset vertical section through the arrangement according to FIG. 17A;

FIG. 17D shows a diagram of the axes in the relaxed position; and

FIG. 18 shows a superposed diagram of the axes in the rest and relaxed positions.

EXEMPLARY EMBODIMENT

A detailed description of an exemplary embodiment will be given hereinbelow, with reference to the accompanying drawings, in respect of the mechanism according to the invention and the function thereof.

The following applies to the rest of the description. If, in order to avoid ambiguity in the drawings, a figure contains designations which are not explained in the directly associated text of the description, then you are referred to the point at which they are mentioned in previous descriptions of the figures. For reasons of clarity, components are not usually designated again in subsequent figures, provided that it is clear from the drawings that they are “recurring” components.

FIGS. 1A to 1C

The mechanism 2 according to the invention is positioned on a height-adjustment pneumatic spring 12 which is plugged, by way of its upright tube 11, in a stand 10, which is typically provided with floor-going elements 13—in particular in roller form. The stand 10, which in this case is star-shaped, forms a substructure 1 along with the upright tube 11, the height-adjustment pneumatic spring 12 and the floor-going elements 13. The top end of the height-adjustment pneumatic spring 12 is plugged in a basically shell-like base 20, which constitutes the lowermost component of the mechanism 2 and accommodates the seat carrier 22 positioned on it. A plate-like front lever 21, into which an arresting element 218 projects, on the one hand is articulated on the front region of the base 20 and, on the other hand, grips beneath the front region of the seat carrier 22. A first lever 31 for adjusting the pre-stressing of the mechanism 2 projects out of the seat carrier 22 on one side, while a second lever 32 for adjusting the depth of the seat 4 and a third lever 30 for actuating the height-adjustment pneumatic spring 12 extend on the other side. The seat 4 essentially comprises a bottom upholstery panel 40 and the upholstery pad 46 arranged thereon. In the embodiment shown, a respective side member 6 is articulated on both sides of the mechanism 2, from the outside, the side member being angled upward and bearing a respective armrest support 71, on which is fastened an armrest 7 with the upholstery pad 70 on top. The backrest 5 is accommodated between the side members 6.

In the rest position according to FIG. 1B, the top side of the seat 4 is located in the state of quasi horizontal seat inclination S₀ and the backrest 5 is in the associated state of more or less vertical backrest inclination R₀. In the relaxed position according to FIG. 1C, the top side of the seat 4 has moved into the state of maximum seat inclination S_(max) and the backrest 5 has synchronously assumed the state of maximum backrest inclination R_(max). The inclination of the seat 4 can thus be altered via the seat angle α, while the inclination of the backrest 5 varies via the backrest angle β.

FIGS. 2A and 2B

The mechanism 2 is made up essentially of the following subassemblies:

-   -   a base 20 with the two first axial rods A1, the buffer part 209         and the two caps 2033;     -   a front lever 21 with the third axial rod A3, the arresting         element 218, the rocker 219, the adjusting screw 2190 and the         bushings 236;     -   a seat carrier 22 with the screws 2209;     -   a gear mechanism 25;     -   a pneumatic spring 26;     -   an intermediate component 27 with the bushings 236;     -   two spring units 28;     -   two bearing strips 29;     -   a third lever 30 with the rod 300;     -   a first lever 31 with the rod 310;     -   a first variant of backrest carrier 23 or a second variant of         backrest carrier 23′ with the two first axial rods A1, which are         positioned along the first axis of rotation D1, the bushings 236         and the fifth axial rod A5, which ends up located along the         fifth axis of rotation D5;     -   a first variant of backrest lever 24 or a second variant of         backrest lever 24′ with the fourth bushings 246, the sixth axis         of rotation D6 and, parallel thereto, the seventh axis of         rotation D7 extending through the backrest levers 24, 24′;     -   an optional pair of side members 6, through which the first axis         of rotation D1 and the seventh axis of rotation D7 extend; and     -   an upholstery panel 40 which does not allow seat-depth         adjustment or an upholstery panel 40′ which does allow         seat-depth adjustment.

FIGS. 3A and 3B

The base 20 has, in the first instance, a floor 200, a first side wall 201, which is adjacent to the floor, a second side wall 202, which is located opposite the first, a front wall 203 and the conical holder 204, which is positioned centrally at the rear and has the central wall 205 running around it in a U-shaped manner. Rising up from the floor 200, in front of the conical holder 204, are two elevated bearing webs 206 which are directed toward one another in the manner of blocks and each has a hole 2060 for accommodating the second axial rod A2, through which the second axis of rotation D2 extends. Located between each bearing web 206 and the adjacent side wall 201,202 is a bearing 207, which is formed from hollowed ribs which rise up from the floor 200 and terminate significantly beneath the holes 2060. Attached to the rear of the two rear extensions 2013,2023 of the side walls 201,202 in each case, at a distance therefrom, is an inner wall 208, and a respective cavity is therefore produced between the extensions 2013,2023 and the side walls 201,202. Stabilizing crosspieces 2051 extend between the central wall 205 and the conical holder 204, with its inner cone 2040. Provided at the start of each of the extensions 2013,2023 is a hole 2012, which is aligned with a hole 2050 in the central wall 205, this hole being aligned, in turn, with a hole 2080 in the inner wall 208. The hole 2080 is followed by an eyelet 2081, which is located in the respective cavity between the inner wall 208 and the associated side wall 201,202. The aligned holes 2012,2080,2050 form, along with the eyelet 2081, a respective holder for the two first axial rods A1 along the first axis of rotation D1. A block-form bearing means 2082 is positioned between the conical holder 204 and the second side wall 202.

Toward the front, the two side walls 201,202 terminate in each case in a front eyelet 2031, and the front wall 203 is located between the same. Respectively aligned holes 2032 extend through the two front eyelets 2031 for the purpose of accommodating the third axial rod A3, which ends up located along the third axis of rotation D3. A respective cap 2033 is provided in order to close the holes 2032 on the outside, with the axial rod A3 inserted.

FIGS. 4A and 4B

The plate-like front lever 21 essentially comprises, in the first instance, the floor 210, the side walls 211, which are arranged to the floor at an angle thereto and have a basically triangular blank, and the two longitudinal webs 212, which run parallel to one another on the underside of the floor 210. The longitudinal webs 212 merge, on the one hand, into a first eyelet 214 and, on the other hand, into a second eyelet 216 in each case. An outwardly curved, shell-like axial web 213 extends between the two first eyelets 214, each eyelet 214 having a hole Z15 and the third axis of rotation D3 running through the two aligned holes 215. Each second eyelet 216 has a hole 217, the two holes 217 being aligned with one another and the fourth axis of rotation D4 extending through the same. From the region of the second eyelet 216, the height of the side walls 211 rises in the direction of the first eyelet 214. Between the two second eyelets 216, the floor 210 has a cutout 2100, in which the arresting element 218 ends up located.

FIGS. 5A and 5B

The seat carrier 22 along with the floor 220, the two downwardly extending side walls 221,222 and the rear wall 223, which connects the side walls 221,222 on one side, form a kind of cover in relation to the base 20. The side walls 221,222 start vertically on the underside of the floor 220, offset in the inward direction from the outer edges. Parallel to the rear wall 223, a stop strip 226 of relatively low height rises up from the underside of the floor 220 and, furthermore, reinforcing ribs 225 are provided between the side walls 221,222 and the underside of the floor 220. A multiplicity of first screwholes 229 run through the floor 220, and a mating contour 2299 rises up on the top side, as it were, above the rear wall 223. An arrangement of notches 227 is located on the top side of the floor 220, along an edge which is offset in the inward direction. The first side wall 221 has a through-opening 224. In the two strip-like outer regions, the floor 220—as seen from the front in the direction of the rear wall 223—has, arranged symmetrically in relation to one another in each case, a second screwhole 228, an upwardly projecting threaded cone 2291 and, behind the through-opening 224, a third screwhole 2292, a further second screwhole 228, a further threaded cone 2291 and, finally, a further third screwhole 2292.

FIGS. 6A to 6D

The gear mechanism 25 comprises a first housing part 250, a second housing part 251, a drive element 252, a spindle screw 253, an eighth axial rod A8, containing the internal thread 254, and in each case two second bushings 225 and two third bushings 256. The first axial hole 2502 and the second axial hole 2503 run horizontally through the housing part 250, and are aligned with the ninth axis of rotation D9 and the second axis of rotation D2, respectively. A cylinder attachment 2500, which has a central through-passage 2501, projects horizontally outward from the housing part 250. Screwholes 2507 are provided on the inside. The second housing part 251 has screwholes 2517 passing right through it and also a first axial hole 2512, which is located along the axis of rotation D9, and a second axial hole 2513, which is located along the axis of rotation D2 and is congruent with the screwholes 2507 and the axial holes 2502,2503. A collar 2514 rises up from the inside and a hollowed guide 2515 is located beneath it, with a slot 2516 being located beneath the guide.

In the assembled state, the screwholes 2507,2517 serve for connecting the two housing parts 250,251. The first bevel wheel 2524 of the drive element 252 is located in the bearing hollow 2504 and its shank 2520 projects into the cylinder attachment 2500, in which case the polygonal socket 2521 in the shank 2520 is accessible via the through-passage 2501. The collar 2514 retains the drive element 252 in position and the second bevel wheel 2534 of the spindle screw 253 engages in the first bevel wheel 2524, the spindle screw 253 being located in the guide 2515 and engaging in the internal thread 254 of the axial rod A8 by way of its external thread 2535. The axial rod A9 passes through the axial holes 2502,2512 and respectively projects out of the housing part 250,251. The third bushings 256 are plugged into the second axial holes 2503,2513 from the outside in each case. The pneumatic spring 26, which can be articulated on the gear mechanism 25 along the eighth axis of rotation D8, has, at one end, a U-shaped clamp part 261, and the axial rod A8, which is thickened in the center and has a threaded stub 2540 on the outside in each case, is plugged into the through-passage holes of this clamp part. A second bushing 255 is screwed onto each threaded stub 2540, and the clamp part 261 is therefore clamped in, a respective bushing head 2550 ending up located in the slot 2516 and/or in the complementary slot of the first housing part 250. The elongate cylinder 260 of the pneumatic spring 26 starts at the clamp part 261 and the piston rod 262 passes out of this cylinder, the piston rod being fastened on the intermediate component 27 by means of a connection 263 which belongs to this intermediate component.

The intermediate component 27 has, in the first instance, a horizontal bolt 274, with a respective blind hole 270 provided on both sides. The fourth axis of rotation D4 runs in the direction in which the two blind holes 270 extend. A fork segment 271 extends downward from the center of the bolt 274 and, at the free ends of the two parallel wings, has in each case two bores serving for accommodating the first and second axial pins 272,273. By means of the second axial pin 273, a rocker 219 is fixed for tilting action between the two wings of the fork segment 271, within a cutout. The rocker 219 projects into a centrally positioned cutout in the bolt 274 and terminates in alignment with the piston rod 262. The arresting element 218 is fastened for a tilting action by means of the first axial pin 272, which likewise runs through the fork segment 271. At that end which projects into the bolt 274, the rocker 219 is provided with an adjusting screw 2190, which is directed toward the end of the piston rod 262 of the pneumatic spring 26 and, there, presses against the valve stem, which is guided in the piston rod 262 and is subjected to spring pre-stressing.

FIGS. 7A and 7B

A spring unit 28 comprises a first spring guide 280, a second spring guide 285 and the helical spring 289, which is accommodated therebetween. A first bearing head 281 is provided on the first spring guide 280 and the first shank 282, from which a pin 283 extends axially, starts at the bearing head 281. The second spring guide 285 has a second bearing head 286, at which the second shank 287, which has an axial hole 288, starts. In the assembled state, the pin 283 is plugged in an axially movable manner in the hole 288 and the ends of the helical spring 289 are seated on the shanks 282,287. When the spring unit 28 is compressed to the maximum extent, the front edges of the shanks 282,287 strike against one another and thus limit any further spring displacement. The outer ends of the bearing heads 281,286 are rounded, the eleventh axis of rotation D11 extending through the first bearing head 281 and the tenth axis of rotation D10 running through the second bearing head 286.

FIGS. 8A and 8B

The pair of bearing strips 29—in the form of, as it were, a right-hand and left-hand bearing strip 29—each have a horizontal floor 290 and a side wall 291 projecting downward on the outside. At the front, the bearing strip 29 terminates with a first eyelet 292, which merges laterally into a stub attachment 2920, from which a stub extension 2921 extends axially—along the fourth axis of rotation D4. Fitted between the side wall 291 and the floor 290 are reinforcing ribs 2900 and a bearing block 293 with a bearing hollow 2930. At the other end, the bearing strip 29 has a second eyelet 297 with the hole 298 passing through it horizontally—the axis of rotation D6 extends through this hole—and with the end noses 2970. Located on the underside of the floor 290, in front of the second eyelet 297, is a third eyelet 294 with the hole 295, through which the axis of rotation D9 runs. On both sides of the third eyelet 294, reinforcing ribs 2900 extend to the side wall 291. A through-opening 2910 is located in the side wall 291 of the right-hand bearing strip 29, in the vicinity of the second eyelet 297. In the vicinity of the two outer eyelets 292,297, a respective screwhole 299 is provided in the floor 290, while the central eyelet 294 has a screwhole 299 on both sides. A further screwhole 299 opens out on the top side of the floor 290 and extends into the bearing block 293.

FIG. 9A

The first variant of backrest carrier 23 is, in principle, a U-shaped sheet-metal part having the floor 230 and, on both sides, outer angled portions, which are parallel to one another and form side walls 231. In each case two aligned front axial holes 232 and rear axial holes 235 extend through the two side walls 231. During assembly, the first bushings 236 are positioned on the front axial holes 232 from the outside by way of their flange side, the bushing shanks being intended for insertion into the eyelets 2981 and for accommodating the axial rods A1, which end up located along the axis of rotation D1. In the vicinity of the axis of rotation D1, a stop 233 is bent upward from the floor 230. The floor 230 contains two holes 234 in line with the stop 233. The rear axial holes 235 serve for accommodating the axial rod A5, which is located along the axis of rotation D5.

FIG. 9B

The second variant of backrest carrier 23′ is an angled component having the floor 230′ and, on both sides, outer angled portions, which are parallel to one another and form side walls 231′. A first leg 237′ is followed by an upwardly directed second leg 238′. In the region of the first leg 237′, in each case two aligned front axial holes 232′ and rear axial holes 235′ extend through the two side walls 231′. During assembly, the first bushings 236, in turn, are positioned on the front axial holes 232′ from the outside by way of their flange side, the bushing shanks being intended for insertion into the eyelets 2981 and for accommodating the axial rods A1, which end up located along the axis of rotation D1. At the transition between the legs 237′,238′, the floor 230 contains a hole 234′. The rear axial holes 235′ likewise serve for accommodating the axial rod A5, which is located along the axis of rotation D5.

FIG. 10A

The first variant of backrest lever 24 comprises the axial rod A6, through which the axis of rotation D6 extends, and the sleeve component 240, which is arranged parallel to the axial rod A6, the axial rod A6 and sleeve component 240 being connected by two upwardly bent arms 242 which are parallel to one another. A through-passage 241 and the axis of rotation D5 run through the sleeve component 240. Fourth bushings 246, of which the flange sides limit the push-in depth of the bushings 246, are provided for insertion into the outer mouth openings on both sides of the through-passage.

FIG. 10B

The second variant of backrest lever 24′ comprises the axial rod A6, through which the axis of rotation D6 extends, and the axial rod A7, which is arranged parallel to the axial rod A6, the axial rods A6,A7 being connected by two upwardly bent arms 242′ which are parallel to one another. The ends of the axial rods A6,A7 project beyond the arms 242′ on both sides, the axial rod A7 terminating as a tapered stub 241′ on both sides. The fourth bushings 246 serve for positioning on the stubs 241′, and the bushing shanks are oriented outwards.

FIG. 10C

The pairs of side members 6 are made up of a first branch 60 and of a second branch 63, which is bent upward from the first branch and has a connection contour 630 for fastening the backrest 5. A horizontal blind hole 601 is provided in the freely terminating head 61 and extends along the axis of rotation D1. An inwardly directed stub 62 containing the blind hole 620, which extends along the axis of rotation D7, projects approximately centrally from the first branch 60.

FIG. 11A

The rectangular upholstery panel 40 is used when there is no need for seat-depth adjustment. The top side of the two longitudinally running outer edges is provided in each case with a lower stepped portion 43. Two internally threaded cones 44 and adjacent holes 48 are provided on each stepped portion 43.

FIGS. 11B and 11C

The likewise rectangular upholstery panel 40′ is used when seat-depth adjustment is desired. The corner regions contain slots 41′, which have a keyhole-like contour on the underside. A screwhole 42′ opens out on the underside in each case adjacent to the slots 41′. On the rear narrow side, the upholstery panel 40′ has a securing contour 45′ for interacting with the mating contour 2299 on the top side of the seat carrier 22.

FIGS. 12A and 12B

The front lever 21, then, is articulated, along the axis of rotation D4, on the intermediate component 27, which is connected to the pneumatic spring 26, the bolt 274 being located in the direction in which the axis of rotation D4 extends. The fork segment 271, which is directed downward from the bolt 274, and the arresting element 218, which is fixed on the fork segment, are arranged partially within the cutout 2100 in the floor 210 of the front lever 21. In that position of the arresting element 218 which is shown, the arresting element has been tilted into the bottom switching position, which provides the rocker 219 with free space, in which case the valve stem can move against the yielding adjusting screw 2190. The pneumatic spring 26 is arrested as a result. On switching over, the rocker 219, with the adjusting screw 2190 seated therein, is pressed onto the valve stem, which is displaced, counter to the pre-stressing, in the direction of the pneumatic spring 26, as a result of which the arresting action is eliminated. Both switching states are stable.

FIGS. 13A to 13H

This sequence of figures portrays the successive steps for assembling the mechanism 2, and the interaction of the components thereof, in combination with the first variant of backrest carrier 23.

First Construction Phase (FIG. 13A)

The front lever 21 is moved into position in the base, between the two front eyelets 2031, by way of the axial web 213 and the two first eyelets 214, in which case the holes 2032,215 are aligned with one another and the axial rod A3 can be pushed in, as a result of which the axis of rotation D3 is rendered functional and the front lever 21 can be pivoted. In order to reduce metallic friction, first bushings 236 are positioned between the front eyelets 2031 and the first eyelets 214 and are pushed onto the axial rod A3. In order to cover the pushed-in axial rod A3, the caps 2033 are pushed into the holes 2032. On the rear part of the base 20, between the extensions 2013,2023, the backrest carrier 23 is pushed in, with the front axial holes 232 in front, until these axial holes 232 are aligned with the holes 2012,2050,2080 and the axial rods A1 can be pushed in from both sides in order to form the axis of rotation D1. In order to reduce the metallic friction, the first bushings 236 are positioned between the side walls 231 and the inner walls 208 and are pushed onto the axial rods A1. The backrest carrier 23 can then be pivoted about the axis of rotation D1. The rod 300 of the third lever 30, for actuating the height-adjustment pneumatic spring 12, is fixed on the bearing means 2082 by way of a holding-down means 301, the rod 300 projecting outward through the through-opening 2021. A buffer part 209 is inserted between the bearing webs 206 and in front of the conical holder 204. In the rest position, the stop 233 strikes against the central wall 205 and thus prevents forward inclination of the seat 4 and backrest 5.

Second Construction Phase (FIG. 13B)

The previously assembled gear mechanism 25 along with the pneumatic spring 26, mounted thereon, and the intermediate component 27 are moved into position between the bearing webs 206 such that the second axial holes 2503,2513 are aligned with the holes 2060, in order for the axial rod A2 to be pushed in. The gear mechanism 25 can thus be moved about the axis of rotation D2. The intermediate component 27, which is attached to the pneumatic spring 26, is located between the second eyelets 216. In order to reduce friction, bushings 236 are introduced between the second eyelets 216 and the bolt 274 of the intermediate component 27. The fastening of the intermediate component 27 between the second eyelets 216 will be explained in respect of FIG. 13E.

Third Construction Phase (FIG. 13C)

The two spring units 28 are positioned in the bearings 207 by way of their bottom, second bearing heads 286, in which case the axis of rotation D10 is produced at the bottom, projecting through the second bearing heads 286, and the axis of rotation D11 is created at the top, projecting through the first bearing heads 281.

Fourth Construction Phase (FIG. 13D)

In order to insert the backrest lever 24 into the backrest carrier 23, the through-passage 241 is brought into alignment with the rear axial holes 235, in which case the axial rod A5 can be pushed in. In order to reduce friction, bushings 246 are inserted between the sleeve component 240 and the side walls 231. The backrest lever 24 can thus be pivoted about the axis of rotation D5, while the axial rod A6 of the backrest lever 24 will form the axis of rotation D6.

Fifth Construction Phase (FIG. 13E)

The bearing strips 29 are joined, from both sides, onto the mechanism 2, which has been pre-assembled thus far. In this case, the stub attachments 2920 end up located in the holes 217 and the stub extensions 2921 each engage in a blind hole 270 in the bolt 274 of the intermediate component 27. Those ends of the axial rod A9 which project out of the gear mechanism 25 on both sides project into the holes 295 in the third eyelets 294 of the bearing strips 29. The ends of the axial rod A6 of the backrest lever 24 end up located in the holes 298 of the second eyelets 297. Moreover, the first bearing heads 281 of the two spring units 28 are positioned in the bearing hollows 2930 on the underside of the bearing strip 29 and thus create the axis of rotation D11. The bearing strips 29 particularly advantageously consist of plastic, while the components which are connected thereto are metallic, and this therefore results in, as it were, self-lubricating bearing locations.

Sixth Construction Phase (FIGS. 13F to 13H)

Finally, the seat carrier 22 is fitted, screw connection taking place from above through the first screwholes 229, which are located in the inner region of the floor 220 and are distributed congruently in relation to the screwholes 299 located in the bearing strips 29. In order to actuate the gear mechanism 25 for adjusting the pre-stressing of the mechanism 2, the rod 310 (see FIG. 2A) has been pushed into the through-passage 2501 and, further, into the polygonal socket 2521. Through the lateral hole 224 in the seat carrier 22, the first lever 31 is pushed onto the outwardly projecting end of the rod 310 in order, by virtue of the latter being rotated, to rotate the drive element 252, which carries along the spindle screw 253 in order thus to move the axial rod A8 upward or downward and, ultimately, to adjust the leverages in the mechanism 2. With the axis of rotation D8 lowered to the maximum extent, the chair is set for lighter individuals, while the axis of rotation D8 moved upward to the maximum extent is the setting for heavier individuals.

The third screwholes 2292, which are provided in pairs on each side of the seat carrier 22, are reserved for the optional fastening of armrests 7. The second screwholes 228, which are likewise provided in pairs, are used for the screw connection from beneath to the non-adjustable upholstery panel 40. Upon installation of an upholstery panel 40′, which can be adjusted in respect of seat depth, screws are screwed into the threaded cones 2291 from above, the screwheads being introduced through the keyhole-like slots 41′ on the underside of the upholstery panel 40′ and thus allowing the upholstery panel 40′ to be displaced.

FIGS. 14A to 14D

This sequence of figures illustrates the use of the second variant of backrest carrier 23′, which is likewise installed in combination with the first variant of backrest lever 24. Articulation along the axes of rotation D1,D5 is basically identical, although, of the backrest carrier 23′, the upwardly projecting second leg 238′ serves for fastening the backrest 5, whereas, in the case of the first variant of backrest carrier 23, connection to the backrest 5 takes place by way of the rectilinearly terminating end.

FIGS. 15A to 15C

An alternative method of fastening the backrest 5 is provided by using the side members 6 in conjunction with a second variant of backrest lever 24′. In this case, the outer ends of the axial rod A6 are likewise accommodated in the holes 298 in the second eyelets 297 in the bearing strips 29 and form the axis of rotation D6 there. The outer stubs 241′ of the axial rod A7 are plugged, with the introduction of bushings 246, into the blind holes 620 in the stubs 62 on the side members 6 and form the axis of rotation D7. The heads 61, with their blind holes 610, of the side members 6 are articulated, along the axis of rotation D1, on the outsides of the two side walls 201,202 of the base 20.

FIGS. 16A to 16D

With the exception of the height adjustment and free rotary movement, the base 20 is fixed in each position on the substructure 1. In the rest position, the seat carrier 22 is located horizontally and the backrest 5 is located approximately vertically. The axis of rotation D4 is arranged to the maximum extent in front of the axis of rotation D3, which cannot be changed in position, and the front lever D21 assumes minimal oblique positioning in relation to the horizontal. The axis of rotation D11 is arranged to the maximum extent in front of the axis of rotation is D10 and the spring units 28 assume minimal oblique positioning in relation to the horizontal. The axis of rotation D9, the axis of rotation D2, which cannot be changed in position, and the axis of rotation D8, are located basically vertically one above the other. The axis of rotation D6 is located at a maximum height level above the axis of rotation D1, which cannot be changed in position, with the smallest possible vertical offset in relation to the axis of rotation D5, which at this point in time is located at the maximum height level. With the axis of rotation D8 moved all the way downward, the piston rod 262 of the pneumatic spring 26 is extended to the maximum extent and the lever arm between the axes of rotation D2,D8 is likewise maximum, in which case it is sufficient for the individual sitting on the chair to apply a relatively small force in the rearward direction in order to move into the relaxed position. If the axis of rotation D8 were moved all the way upward, the piston rod 262 of the pneumatic spring 26 would be extended to a lesser extent and the lever arm between the axes of rotation D2,D8 would be shorter, in which case the individual sitting on the chair would need to apply a higher force in the rearward direction in order to move into the relaxed position, as is generated by a heavier bodyweight.

FIGS. 17A to 17D

In the relaxed position, the seat carrier 22 rises up at the front, slopes down to the rear and moves in the direction of the backrest 5, that is to say it assumes an oblique position at the same time as the backrest 5 is inclined rearward. This pre-supposes that the pneumatic spring 26 is in the non-arrested switching position, that is to say the arresting element 218 has been tilted upward. The axis of rotation D4 is not as far in front of the axis of rotation D3, which cannot be changed in position, and the front lever 21 assumes maximum oblique positioning in relation to the horizontal. The axis of rotation D11 is arranged to the minimum extent in front of the axis of rotation D10 and the spring units 28 assume maximum oblique positioning in relation to the horizontal. The axis of rotation D9 has moved behind the axis of rotation D2, which cannot be changed in position, while the axis of rotation D8 is now arranged in front of the axis of rotation D2. The axis of rotation D6 is located at the minimum height level above the is axis of rotation D1, which cannot be changed in position, with the greatest possible vertical offset in relation to the axis of rotation D5, which at this point in time is located at the lowermost height level. The spring units 28 are compressed to the maximum extent and the piston rod 262 of the pneumatic spring 26 is retracted to the maximum extent, in which case, with a defined reduction in load, the backrest 5 and the seat carrier 22 with the seat 4 are automatically forced back into the rest position.

FIG. 18

This superposed diagram of the axes in the rest and relaxed positions portrays the axes of rotation D1,D2,D3, which cannot be changed in position and are also depicted here in solid black, and the positions of the essential axes of rotation D4,D5,D6,D8,D9, which can be changed in position, as they move around the axes of rotation D1,D2,D3. Not shown here are the axis D11, which is located in the spring units 28 and likewise changes in position, and the bottom axis D10, which runs through the spring units 28 but, in contrast, barely changes in position. If use is made of a pair of side members 6, the position of the axis of rotation D7 also changes. 

1. A mechanism (2) for a chair, in particular for a rotatable office chair with a pneumatic spring (12) which is arranged vertically in the substructure (1) and has a telescopically extensible piston rod for adjusting the height of a seat (4), whereas: a) the inclining adjustment of the seat (4) is synchronous with an inclining adjustment of a backrest (5); b) the mechanism (2) has a fixed base (20), through which a fixed first axis of rotation (D1) extends and on which an inclinable seat carrier (22) is mounted; c) arranged between the base (20) and the seat carrier (22) is a front connecting means (21), which is articulated along a fixed third axis of rotation (D3) on the base (20) and along a movable fourth axis of rotation (D4); d) a rear connecting means (24,24′) is provided and is articulated, on the one hand, along a movable sixth axis of rotation (D6) and, on the other hand, along a movable further axis of rotation (D5,D7); e) the mechanism (2) contains at least one first spring element (26), which acts between the base (20) and the seat carrier (22) and is articulated along the fourth axis of rotation (D4), characterized in that f) the first spring element (26) is also articulated along a movable eighth axis of rotation (D8), which can be changed in position by means of a gear mechanism (25) which can be actuated by the user from the outside.
 2. The mechanism (2) as claimed in claim 1, characterized in that a) the gear mechanism (25) is articulated along a fixed second axis of rotation (D2), which extends through the base (20), along the eighth axis of rotation (D8) and along a movable ninth axis of rotation (D9); b) in the rest position, with the seat (4) positioned, at least in principle, horizontally and the backrest (5) located vertically, the second axis of rotation (D2), the eighth axis of rotation (D8) and the ninth axis of rotation (D9) are located at least essentially vertically one above the other, and c) in the relaxed position, with the seat (4) inclined up to a maximum extent and the backrest (5) inclined up to a complementary maximum extent, the eighth axis of rotation (D8) is displaced, in the direction of the third axis of rotation (D3), in front of the second axis of rotation (D2) and the ninth axis of rotation (D9) moves, in the opposite direction, behind the second axis of rotation (D2).
 3. The mechanism (2) as claimed in at least either of claims 1 and 2, characterized in that a) the first spring element (26) is a pneumatic spring (26) with a cylinder (260) and a telescopically extensible piston rod (262); b) the piston rod (262) is extended to the greatest extent in the rest position, with the eighth axis of rotation (D8) moved all the way downward, and is retracted to the greatest extent in the relaxed position, with the eighth axis of rotation (D8) moved all the way upwards; and c) the piston rod (262) is articulated along the fourth axis of rotation (D4) by means of an intermediate component (27).
 4. The mechanism (2) as claimed in at least one of claims 1 to 3, characterized in that a) the mechanism (2) contains, within it, pairs of spring units (28) which are supported, on the one hand, in a bearing (207) of the base (20) and, on the other hand, beneath bearing strips (29), in bearing blocks (293), the bearing strips (29) being joined to the base (20) from both sides; and b) the bearing strips (29) preferably consist of plastic and thus form self-lubricating bearing locations along with the joined-on, preferably metallic components.
 5. The mechanism (2) as claimed in at least one of claims 1 to 4, characterized in that a) the front connecting means (21) is designed as a plate-like lever, through which the axes of rotation (D3,D4) extend; and b) the rear connecting means (24,24′) comprises a sixth axial rod (A6) and a sleeve component (240), which is connected thereto via arms (242), or a sixth axial rod (A6) and a seventh axial rod (A7), which is connected thereto via arms (242′), the associated axes of rotation (D5,D6,D7) extending through these axial rods.
 6. The mechanism (2) as claimed in at least one of claims 1 to 5, characterized in that a) a backrest carrier (23,23′) can be articulated along the axis of rotation (D1), within the base (20), or a pair of side members (6) can be articulated outside the base (20), in order for the backrest (5) to be fastened thereon; and b) the bearing strips (29) have stubs (2920,2921) for penetrating into the front lever (21) and the intermediate component (27), and they also have mounts (295,298) for accommodating the ninth axial rod (A9), which passes through the gear mechanism (25), and for accommodating the sixth axial rod (A6).
 7. The mechanism (2) as claimed in at least one of claims 1 to 6, characterized in that a) an arresting element (218), which can be actuated by the user, is arranged on the intermediate component (27) for blocking the pneumatic spring (26) with optional switching functions; and b) the arresting element (218) acts on a valve stem which is guided in the piston rod (262) of the pneumatic spring (26). 